A large collection of music toys can be found on the page of Andre Michelle with interesting concepts of sequencers. My favorite is “Pulsate”: http://lab.andre-michelle.com/pulsate Place at least 2 circles on the desk and they will grow until they collide. Depending on the dimension of the circles they generate a tonal sound during the collision. A similar app is available on http://www.earslap.com/projectslab/circuli . Indeed an awesome generative music generator.